3.1

Fossil (Crustacea, , Brachyura) from Lothagam

Joel W. Martin and Sandra Trautwein

Remains of crabs attributable to the family Potamonautidae have been recovered from the Nawata Formation and the Apak Member of the Nachukui Formation. Their occurrence in the Lothagam se­ quence is consistent with the presence of a weU-oxygenated riverine system. More precise identification requires access to features not normally preserved in fossil material.

Freshwater crabs are a tremendously diverse assemblage dae) in its own superfamily Pseudothelphusoidea, and of true (brachyuran) crabs known firom Central and six Old World freshwater families. The Old World South America, Africa (including Madagascar), Aus­ families are partitioned among the superfamilies Ge- tralasia, southern Europe, and south and Southeast carcinucoidea (famihes Gecarcinucidae and Parathel- Asia. There are an estimated 900 species in the group, phusidae) and (families Deckiniidae, Pla- making them one of the most diverse assemblages of tythelphusidae, Potamidae, and Potamonautidae (table crabs. Species are known from cold, rapidly flowing 3.1). Many formerly recognized families have been syn- mountain streams, tropical rainforest floors (where they onymized in recent years (see discussion in Martin and may even be semiterrestrial or arboreal), warm lowland Davis 2001). ponds and paddies, and just about any other freshwater Details of the timing of the invasion of freshwater by environment (Ng 1988; Rodriguez 1982, 1992; Cum- these crabs remain unclear. Hypotheses range from 11 berHdge 1991; Cumberlidge and Sachs 1989a, 1989b). independent unrelated invasions of freshwater by dif­ Their diversity, range, and size make them important ferent groups of marine crabs during the Late Creta­ ecologically, economically, and medically (as vectors of ceous to lower Tertiary (e.g., Bott 1970a, 1970b; Pretz- some tropical diseases). Although they were originally mann 1973), to two lower Tertiary invasions (one in thought to comprise a single family (Potamidae), the the Americas that resulted in the and group was treated as 11 families in three superfamOies another one elsewhere that led to all other families from by Bott (1970a, 1970b) andPretzmann (1972,1973). In some widespread marine ancestor; see Sternberg et al. turn. Bolt's and Pretzmann's work has been questioned 1998), to a single, much older (~200 Ma) colonization by more recent workers who employ cladistic meth­ of the freshwater habitat; this resulted in freshwater crab odology that is based on new morphological and mo­ monophyly (e.g., Rodriguez 1986; Ng et al. 1995). lecular sequence data (e.g., Guinot et al. 1997; Cum­ In Africa, only the superfamily Potamoidea is berlidge 1999; Sternberg and Cumberhdge 1999; Abele known. (The superfamily Pseudothelphusoidea is re­ et al. 1999). The taxonomy and phylogeny of the group stricted to Central and South America, as is the family are actively being revised on the basis of some of these Trichodactylidae of the otherwise marine superfamily new data. In this contribution, we follow the admitted- ; the two families of the . ly conservative classification of Martin and Davis are restricted to the Indian subcontinent, Southeast (2001), where the freshwater crabs are composed of one Asia, and Australasia). Of the four currently recognized family (Trichodactylidae) in the otherwise marine su- potamoid families (Martin and Davis 2001), the Pla- perfamily Portunoidea, one family (Psuedothelphusi- tythelphusidae are restricted to Lake Tanganyika, and 68 Joel W. Martin and Sandra Trautwein

the Potamidae are found in northwest Africa, south­ ably members of the family Potamonautidae. The "al­ eastern Europe, and Asia (figure 3.1). most complete lack of a fossil record for all groups of Thus, with some certainty we can say that the fossil African freshwater crabs" (Sternberg and Cumberlidge crabs from Lothagam could only belong to one of two 1999:493) makes comparisons with existing fossil ma­ families: Potamonautidae (known only from sub- terial virtually impossible. In this report we give brief Saharan Africa plus the Nile in Egypt and from Mada­ descriptions of fossil freshwater crabs from the Late gascar) and Deckeniidae (known only from East Af­ Miocene hominid-bearing locality of Lothagam, Kenya, rica). Species identifications in these families often are that were collected during the 1991 and 1992 field sea­ based on the detailed structure of the male pleopods sons. Catalog numbers for these specimens begin with (among other features), such that even remarkably pre­ the acronym KNMI-LT, which denotes invertebrate served could not be identified further (that is, to fossils from Lothagam in the collections of the National the level of genus or species). We are assuming that all Museums of Kenya, Nairobi. of the Lothagam fossils are members of the freshwater crab superfamily Potamoidea and that, based on the modern-day distribution of this family, they are prob- Materials and Methods

We examined 32 specimens that represented parts of fossil crabs from Mio-Pliocene strata exposed at Loth­ agam. These samples derived from both members of the Nawata Formation and from the Apak Member of the Nachukui Formation; thus, they ranged in age from 4.2 to 7.4 Ma (McDougall and Feibel 1999). By far the ma­ jority of the specimens comprised extremities and mid­ sections of the fingers of the chelipeds, including both dactylar and propodal finger pieces. Occasional larger specimens contained fragments of carapace, but none was complete enough to allow positive identification, even to the family level. Specimens selected for photog­ raphy were lightly cleaned with a dry paintbrush. Ob­ servations and line illustrations were made with a Wild M5 APO stereomicroscope. Measurements were made with digital calipers and rounded to the nearest tenth of a millimeter.

Systematic Description

Superfamily Potamoidea

The superfamily Potamoidea contains four families, two of which—Deckiniidae and Potamonautidae—occur today in East Africa.

Family Potamonautidae Figure 3.1 Two of the more complete fossil crab fragments from Lothagam. Top = KNMI-LT 23667, Upper Nawata, Most characters that serve to distinguish crabs of the posterior two thirds of carapace, dorsal view, with carpus of family Deckiniidae from those of the family Potamo­ right cheliped visible at upper right. Estimated size of entire nautidae involve details of the orbital margins and the crab is carapace width, 38.5 mm; carapace length (estimated fifth pereiopod dactylus (Sternberg and Cumberlidge because of incomplete frontal region), 33.1 mm. Bottom = 1999), features that are not preserved in any of the KNMI-LT 24193, Lower Nawata, ventral view of different specimen with intact left cheliped (in outer view) and with Lothagam fossils. The Deckiniidae contains only the ge­ portions of pereiopods two and three. Length of chela (base nus Deckenia, which currently contains two species, D. of propodus to tip of propodal finger), 28.4 mm; height (just imitatrix and D. mitis (Ng et al. 1995). The group is proximal to articulation of dactylus and propodus), 11.5 mm. characterized by an "ovate carapace" caused by (or fa- Fossil Crabs (Crustacea, Decapoda, Brachyura) from Lothagam 69

cilitating) greatly swollen branchial chambers, which KNMI-LT 24187 comprises the middle portion of a "seems to be associated with terrestrial habits or life in chelipedal finger. Five teeth are visible, the middle being stagnant, poorly oxygenated waters" (Ng et al. largest and approximately twice the height of the other 1995:583). The few fragments of dorsal carapace (e.g., four. Its curvature suggests this is the dactylus of the figure 3.1) revealed no signs of an expanded branchial left chela or possibly the propodus of the right chela region, and thus the genus Deckinia (and the family (less likely). Length 10.0 mm; greatest height (at basal Deckiniidae) have been ruled out. Although we could tooth) 5.4 mm. not detect a clear epigastric crest or a postorbital crest KNMI-LT 24188 consists of a small basal to three- that extends to the epibranchial tooth, both of which fourths length of a left chela dactylus with six low, are reported to characterize species in the Potamonau- rounded teeth on the cutting surface. Length 9.9 mm; tidae (Sternberg and Cumberlidge 1999:505,506), these height 4.6 mm at base. regions of the carapace were very poorly preserved. By KNMI-LT 24189 is a small fragment of only the default, and assuming also that all fossilized pieces sent sclerotized portion (i.e., teeth and immediately adjacent to us came from crabs with similar carapace structure, area) of a right dactylus or left propodus. Nine teeth, of we have assigned all of the Lothagam fossils to the fam­ varying sizes, are visible along the cutting surface. ily Potamonautidae, Arguing against this placement is Length 17.2 mm; greatest height (at approximate level the fact that one chelipedal carpus was preserved ofbasalmost tooth) 3.5 mm. (KNMI-LT 23667; figure 3.1, top), and it appeared to BCNMI-LT 24190 comprises the dactylus and most of possess a single anteromedial spine, whereas potamo- the propodus of a right chela in "outer" view. Length nautids typically have two such spines (Sternberg and 28.5 mm; height 12.3 mm. Cumberlidge 1999; Cumberlidge 1999). KNMI-LT 24191 comprises two claw fragments. The larger (thicker) fragment (length 16.4 mm; greatest height 6.5 mm) appears to be the right propodal finger Potamonautidae gen. and sp. Indet. and bears a row of cutting teeth. These increase in size (Figures 3.1, 3.2) from 1 to 5; tooth 6 is small, tooth 7 is approximately equal to 5, and thereafter the teeth decrease in size to­ Lothagam Material ward the tip. The smaller (thinner) fragment (length 18.5 mm; height 5.1 mm) appears to be dactylar (slen­ • Lower Nawata: 1, dactylus fragment; 24193, claw and der, more curved), but this is not definite. Approxi­ part exoskeleton; 24194, claw and part exoskeleton; mately eight teeth are visible on this fragment, the prox­ 24195, claw fragments; 24196, chela fragment; 24197, imal four of which are larger than the distal four. claw fragment; 25094, Rt. propodal finger; 25095, KNMI-LT 24192 (figure 3.2e) is a large (length 23.5 dactylus; 25100, claw fragment; 25101, chela frag­ mm; height 7.9 mm at base), strongly curved dactylus ment; 25102, chela fragments; 25415, exoskeleton of the right chela and is obviously from a crab that and claw fragment; 25416, limb fragments. possessed a large "gape" when chela fingers were closed. • Upper Nawata: 23667, exoskeleton; 24188, claw frag­ The cutting surface has a row of three or four small, ment; 24190, claws; 24191, 2 claw fragments; 24192, rounded teeth and has minute tubercles distal to the chela fragment; 25087, claw fragment; 25088, claw last tooth. fragments; 25089, exoskeleton; 25090, claw and ex­ KNMI-LT 24193 (figure 3.1) represents an entire left oskeleton fragments; 25091, claw; 25092, chela frag­ chela, most of the cheliped, and the coxa of pereiopods ment; 25093, 3 claw fragments; 25096, chela frag­ 2 and (partial) 3. Part of the thoracic sternum is visible, ments; 25097, propodal finger fragment; 25098, claw showing cuticular punctae. Length of the entire chela fragment; 25099, claw fragment; 25128, dactylus (base of propodus to tip of propodal finger) 28.4 mm; fragment. estimated length of chela plus carpal segment 30.5 mm. • Apak Member: 24187, chela fragment; 24189, claw Greatest height of chela (measured just proximal to fragment. point of articulation of dactylus) 11.5 mm. KNMI-LT 24194 comprises parts of both fingers of KNMI-LT 23667 (figure 3.1, top) is a large specimen, the left chela; additionally, a small piece of the sternal consisting mostly of a badly fractured posterior two- plastron is visible. Length (of entire fossil) 16.8 mm; thirds of carapace and part of the right cheliped. The width of entire fossil 16.8 mm. Greatest length of chela carpus of the right cheliped is striking, with sharp an­ fingers 13.5 mm; height of fingers (combined) 8.2 mm. teromedial and smaller anterolateral spines. Greatest KNMI-LT 24195 contains 13 fragments of chelipedal carapace width 38.5 mm; greatest carapace length (es­ fingers. Two of the fragments are quite large (length.of timated because of deteriorated frontal region) largest 21.5 mm; height 9.9 mm measured from the bot­ 33.1 mm. tom of the first tooth to the top of the finger). 70 Joel W. Martin and Sandra Trautwein

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Figure 3.2 Photographs of representative fossil crab fragments from the Lower Nawata (a-d) and Upper Nawata (e-i). a = KNMI-LT 24196, length = 15.8 mm; b = KNMI-LT 25094, length = 23.2 mm; c = KNMI-LT 25101, length = 23.9 mm; d = KNMI-LT 25102 (two fragments), lengths = 19.7 mm and 17.2 mm; e = KNMI-LT 24192, length = 23.5 mm; f = KNMI-LT 25087, length = 18.0 mm; g = KNMI-LT 25092, length = 15.8 mm; h = KNMI-LT 25097, length = 13.3 mm; i = KNMI-LT 25099, length = 20.5 mm.

KNMI-LT 24196 (figure 3.2a) is a large piece of a with two large teeth and one smaller one between them, chela tip (probably the propodal finger of the right also one small tooth distal to second large tooth. Length chela), one of few that extends to almost the distal ex­ 18.0 mm; height 5.9 mm at basalmost large tooth. tremity. The cutting surface has 12 closely set teeth of KNMI-LT 25088 constitutes two firagments, both in varying sizes; teeth 4 and 7 (proximal to distal) are larg­ poor condition. The larger (length 14.2 mm; height 3.5 est. Length 15.8 mm; height (at basalmost of two large mm at second basal tooth) consists of a row of eight teeth) 7.4 mm. teeth, sizes of which vary; teeth 2 and 4 (proximal to KNMI-LT 24197 is a minute tip of a claw with four distal) are larger than the others. Smaller fragment or five low, well-worn teeth. Length 7.1 mm; height 3.0 length 11.2 mm; height at midpoint 3.4 mm. mm. KNMI-LT 25089 includes part of a fairly large fe­ KNMI-LT 25087 (figure 3.2f) probably represents a male; the abdomen and part of the left chela propodus left dactylus. It consists of a long, thin claw fragment are fairly clear in ventral view. Greatest length of the fossil Crabs (Crustacea, Decapoda, Bra&iyura) from Lothagam 71

left chela 28.1 mm; greatest height 9.9 mm. There is KNMI-LT 25098 is a thick basal portion of right also a partial right dactylus (length 18.0 mm; height chela dactylus. The basal tooth is large and is followed 8.0 mm at base). by seven or more teeth (extremity of finger missing) KNMI-LT 25090 includes six individual fragments of alternating sizes. Length 13.2 mm; height at base of chelipeds. The matrix is extremely hard, and pos­ 7.8 mm. sibly for this reason the specimens appear glossy, much KNMI-LT 25099 (figure 3.2i) is a large piece of more so than in other samples. All specimens are badly what appears to be the right propodal finger of an fragmented; very little information can be gleaned obviously sizeable crab (length 20.5 mm; height 7.4 from them. One notable specimen is a nearly entire mm at second basalmost tooth). Approximately ten claw in "outer view," with the manus ("hand" of the teeth are visible along the cutting edge; the basal-most propodus) broken open and with tips of both fingers two teeth and teeth 5 and 9 (proximal to distal) rise missing. Length of entire chela (fingers and imprint of above the others. propodus) 29.3 mm; height (measured just proximal KNMI-LT 25100 represents the partial dactylus of to articulation with dactylus) 12.3 mm. Other pieces a right chela with a large basal tooth plus eight small are mostly claw and leg fragments. teeth; lots of adhering matrix. Length 20.2 mm; height KNMI-LT 25091 constitutes an extremely large 10.0 mm. (length 25.4 mm; height 11.0 mm at base) dactylus of KNMI-LT 25101 (figure 3,2c) is a large (length a right chela; most of the cutting surface is obscured 23.9 mm; height 9.5 mm at base), curving dactylus of by adhering calcareous matrix. a left chela (possibly the propodus of a right chela, KNMI-LT 25092 (figure 3.2g) represents the prox­ but very delicate if so). Cutting surface with eight imal three-fourths of a right chela dactylus. A large teeth, varying in size but mostly small. basal tooth is followed distally by smaller, then larger, KNMI-LT 25102 comprises two specimens. The then smaller teeth. Eight teeth are visible along the larger is a dactylus of a left chela (length 19.7 mm; cutting surface. Length 15.8 mm; height 8.7 mm at height 7.9 mm at most basal tooth) (figure 3.2d, lower base. photograph); there are two large teeth, with smaller KNMI-LT 25093 comprises three claw fragments. teeth proximally and distally (not between them). The The largest fragment (length 18.7 mm; height 6.4 mm smaller specimen (length 17.2 mm; height 6.6 mm) at base) is gently curving and bears 12 teeth on the (figure 3.2d, upper photograph) is a right dactylus or cutting surface; the teeth are more or less alternate in left propodal finger, with a cluster of three tightly op­ size, medium to small. A second fragment constitutes posed teeth, of which the center one is the largest. a very small (length 10.1 mm; height 4.2 mm) claw KNMI-LT 25128 comprises a midsection of a right tip, either left dactyl or right propodal finger; 13 teeth chela dactylus; the cutting surface has eight visible are present on the cutting surface, with teeth 4 and 6 teeth. Length 11.5 mm; height 7.8 mm at base. larger and sHghtly more acute than the others. The KNMI-LT 25415 comprises two specimens. The third fragment comprises a midsection of a claw tip. (larger) first specimen is a rare "whole crab" fossil, Length 11.9 mm; height 6.5 mm. showing the underside (mostly) and partial upper sur­ KNMI-LT 25094 (figure 3.2b) is a large (length 23.2 face of the carapace, plus part of one cheliped. Some mm; height 8.5 mm at base), heavy, well-formed right sternal plates and sutures are visible, but it is difficult propodal fixed finger, entire nearly to the distal ex­ to enumerate these as the specimen is in very poor tremity. The entire row of teeth on the cutting surface condition. Estimated size of the entire crab is 27.8 is visible; teeth 5 and 9 (proximal to distal) are mark­ mm carapace width. The second specimen is a very edly larger and more acute than the others. thin (probably dactylar) chela finger with approxi­ KNMI-LT 25095 is a thick, blunt finger, clearly the mately seven low, worn teeth. Length 12.4 mm; height dactylus of a right chela, worn, with few details dis­ 3.9 mm at base. cernible. Length 18.0 mm; height 8.4 mm at base. KNMI-LT 25416 includes a nearly complete left KNMI-LT 25096 comprises four small fragments. chela and a large carpal segment (possibly from a dif­ The largest (length 20.6 mm; height 8.8 mm at base) ferent crab). Length of nearly complete chela 21.5 is probably a right chela dactylus. Another is the base mm; height 7.8 mm. Other material includes small of a chela dactylus. pieces of carapace and a partial right cheliped dactylus KNMI-LT 25097 (figure 3.2h) is a small but remark­ (length 15.1 mm; height 9.5 mm at base). There are ably clean fragment of a right propodal finger; it is frag­ also many unidentifiable fragments. ile and hollow. Eighteen teeth are visible along the cut­ KNMI-LTI 1 appears to be a partial left chela dac­ ting surface; teeth 4 and 7 (proximal to distal) are larger tylus; seven teeth are visible near the base of the than the others, some of which are minute, especially cutting surface. Length 17.6 mm; height 10.9 mm at toward the tip. Length 13.3 mm; height 5.0 mm. base. 72 Joel W. Martin and Sandra Trautwein

Paleoenvironmental Interpretation nautidae) from Nigeria. Canadian Journal of Zoology 69: 1938-1944. Cumberlidge, N. 1999. The Freshwater Crabs of West Africa: Had these fossils proven to be members of the East Af­ Family Potamonautidae. Faune et Flore Tropicales No. 35. rican family Deckiniidae, some speculation on habitat Paris: Institut de Recherche pour le Developpement. might have been warranted because the inflated cara­ Cumberlidge, N., and R. Sachs. 1989a. A key to the crabs of pace of deckiniids may reflect a low oxygen environ­ Liberian fresh waters. Zeitschrift fiir Angewandte Zoologie ment (Ng 1988; Ng et al. 1995). The fact that they are 76:221-229. apparently members of the Potamonautidae reveals less Cumberlidge, N., and R. Sachs. 1989b. Three new subspecies of information, as potamonautids are known from a much the West African freshwater crab Liberonautes latidactylus (de Man, 1903) from Liberia, with notes on their ecology. wider range of habitats, virtually throughout sub-Sa- Zeitschrift fiir Angewandte Zoologie 76:425-439. haran Africa and including the Nile River in Egypt, east­ Guinot, D., B. G. M. Jamieson, and C. C. Judge. 1997. Ukra- ern Africa, South Africa (e.g., Stewart 1997; Cumber- structure and relationships of spermatozoa of the freshwater lidge 1999), and parts of Madagascar. In general, crabs and Potatnon ibericiim (Crustacea, however, potamonautids are commonly referred to as Decapoda, Potamidae). Journal of Zoology (London) 241: "river crabs" because of their propensity for these hab­ 229-244. itats. Thus, we may assume that the Lothagam fossil Martin, J. W., and G. E. Davis. 2001. An Updated Classification crabs are indicative of a relatively weli-oxygenated riv­ of the Recent Crustacea. Science Series No. 39. Los Angeles: erine system. Virtually all freshwater crabs, including Natural History Museum of Los Angeles County. the African potamonautids, are opportunistic scaven­ McDougall, I., and C. S. Feibel. 1999. Numerical age control for the Miocene-Pliocene succession at Lothagam, a gers and predators, and thus the presence of these crabs hominoid-bearing sequence in the northern Kenya Rift. in Lothagam ftirnishes Httle information about co- Journal of the Geological Society (London) 156:731-745. occurring species. Ng, P. K. L. 1988. The Freshwater Crabs of Peninsular Malaysia and Singapore. Singapore: Department of Zoology, National University of Singapore, and Shing Lee Publishers. Ng, P. K. L., Z. Stevcic, and G. Pretzmann. 1995. A revision of Acknowledgments the family Deckiniidae Ortmann, 1897 (Crustacea: Deca­ poda: Brachyura: Potamoidea), with description of a new We thank the government of Kenya and the trustees of genus (Gecarcinucidae, Gecarcinucoidea) from the Sey­ the National Museums for permission to study these chelles, Indian Ocean. Journal of Natural History 29: interesting specimens. We thank Neil CumberUdge and 581-600. Pretzmann, G. 1972. Die (Crustacea, Trisha Spears for sharing their thoughts on the origins, Brachyura), Zoologica 42:1-182. distributions, and classification of the modern fresh­ Pretzmann, G. 1973. Grundlagen und Ergebnisse der Syste- water crab famihes. This work was funded in part by a matik der Pseudothelphusidae. Zeitschrift fiir Zoologische U.S. National Science Foundation grant to J. W. Martin Systematik und Evolutionsforschung 11:196~218. and Dave Jacobs (DEB 9978193, PEET program in Sys­ Rodriguez, G. 1982. Les crabes d'eau douces d'Amerique: Famille tematic Biology). des Pseudothelphusidae. Faune Tropicale 22. Paris: ORSTOM. Rodriguez, G. 1986. Centers of radiation of fresh-water crabs In the neotropics. In R. H. Gore and K. L Heck, eds., Bio- geography of the Crustacea, pp. 51-67. Issues 4. References Cited Rotterdam: Balkema. Rodriguez, G. 1992. The Freshwater Crabs of America: Family Abele, L, G., T. Spears, and N. Cumberlidge. 1999. Biogeogra- Trichodactylidae and Supplement to the Family Pseudothel­ phy and phylogeny of freshwater crabs based on molecular phusidae. Faune Tropicale 31. Paris: ORSTOM. evidence. In Program and Abstracts, The Crustacean Society Sternberg, R. von, and N. Cumberlidge. 1999. A cladistic anal­ Summer Meeting, p. 20. Lafayette, Louisiana, 26-30 May ysis oi Platythelphusa A. Milne-Edwards, 1887, from Lake 1999. Tanganyika, East Africa (Decapoda: Potamoidea: Platythel- Bott, R. 1970a. Betrachtungen iiber die EntwicHungsgeschichte phusidac) with comments on the phylogenetic position of und Verbreitung der Subwasser-Krabben nach der Samm- the group. Journal of Natural History 3:493-511. lung des Naturhistorischen Museums in GenffSchweiz. Re­ Sternberg, R. von, N. Cumberlidge, and G. Rodriguez. 1998. vue Suisse de Zoologie 77:327-344. On the marine sistergroups of the freshwater crabs (Crus­ Bott, R. 1970b. Die Subwasserkrabben von Europa, Asien, Aus- tacea: Decapoda). Journal of Zoological Systematics and Evo­ tralien und ihre Stammesgeschichte. Eine revision der lutionary Research 37:19-38, Potamoidea und der Parathelphusoidea (Crustacea, Deca- Stewart, B. A. 1997. Morphological and genetic differentiation poda). Abhandlungen der Senckenbergischen Naturfor- between populations of river crabs (Decapoda: Potamo­ schenden Gesellschafi 526:1~33B, nautidae) from the Western Cape, South Africa, with a tax- Cumberlidge, N. 1991. Sudanonautes kagorensis, a new species onomic revision of Gecarcinautes brincki. Zoological Journal of fresh-water crab (Decapoda: Potamoidea: Potamo­ of the Linnean Society 199:1-21. TABLE 3.1 Classification of Freshwater Crabs' and Their Present-day Distribution

Subphylum Crustacea Order Decapoda Suborder Pleocyemata Infraorder Brachyura Section '' Subsection Family Location Superfamily Portunoidea' Family Trichodactylidae Central and South America Super&mily Pseudothelphusoidea Family Pseudothelphusidae Central and South America Superfamily Gecarcinucoidea Family Gecarcinucidae Indian subcontinent and Southeast Asia Family Parathelphusidae Indian subcontinent, Southeast Asia, and Australasia Superfamily Potamoidea Family Deckiniidae East Africa Family Platythelphusidae Lake Tanganyika Family Potamidae Northwest Africa, southeast Europe, the Middle East, the Himalayas, Southeast Asia, and China Family Potamonautidae Subsaharan Afi-ica (plus the Nile in Egypt) and Madagascar ' Contains a total of three subsections, 20 superfamilies, and 61 families (Martin and Davis 2001). ' Other families of brachyuran crabs have species that can or must live in freshwater (e.g., Metapaulius depressus in the Grapsidae, Vca subcylindrica in the Ocypodidae, and others) but that are not confused with the potamon-like crabs (the former "Family Potamida"). • Contains two other femilies of crabs restricted to marine or estuarine waters.